FIELD OF THE INVENTION
The invention relates to circuits for generating a reference potential. More specifically, the invention pertains to a circuit configuration for generating a reference potential with a first transistor, the emitter of which is connected to a ground potential and the base and collector of which are connected to one another; with a second transistor, the base of which is connected to the base of the first transistor; with a first resistor connected between the collector of the first transistor and an output terminal for picking up the reference potential; a second resistor connected between the collector of the second transistor and the output terminal; with a third resistor connected between the emitter of the second transistor and the ground potential; with a third transistor, the base of which is connected to the collector of the second transistor and the emitter of which is connected to the ground potential; with a fourth transistor, the collector of which is connected to the supply potential, the emitter of which is connected to the output terminal, and the base of which is connected to the collector of the third transistor; a first current source is connected between the base and the collector of the fourth transistor.
One such circuit configuration, also known as a band-gap reference voltage source, is known for instance from Paul R. Gray, Robert G. Meyer, "Analysis and Design of Analog Integrated Circuits", Second Edition 1984, pp. 293-296, and is used in many integrated circuits to supply other circuit blocks with a temperature-independent reference potential and/or a plurality of reference currents. In the future, it will moreover become increasingly important for integrated circuits to operate as independently as possible of the supply voltage, especially for battery-operated devices. In any actual transistor driven with a constant base-to-emitter voltage or a constant base current, the collector current, because of the so-called Early effect, fluctuates as a function of the collector-to-emitter voltage, which is often linked in turn directly to the supply voltage. The Early effect is described for instance in Paul R. Gray, Robert G. Meyer, "Analysis and Design of Analog Integrated Circuits", Second Edition 1984, pp. 17-19. This problem is also critical precisely because fast modern transistors tend to have poor properties in terms of the Early effect.